This invention relates to slipper-boots having improved resistance to tearing and reduced tendency for slipping, which are formed from foamed synthetic polymeric or elastomeric sheeting material. More particularly, the invention relates to a slipper-boot of such material which has longitudinal seams running up its heel and toe portions to its foot-receiving throat and to means for minimizing tearing of the material adjacent such seams. An improved apparatus and method for making such slipper-boots also comprise part of this invention.
In the past, there has been a need for strong, sanitary and inexpensive footwear and for methods and apparatus for manufacturing such articles. To a great extent, U.S. Pat. No. 3,426,454 has met this need by disclosing slippers comprised of two bands of synthetic polymeric sheeting material heat-sealed to each other along a seam extending from the forward edge of the foot opening, along the upper toe of the slipper, back along the sole to the heel and up the heel to the foot opening. To reduce tearing of the material along the seam due to stresses generated when the slipper is donned, the front and rear edges of the foot opening are oriented to meet the seam at an angle.
Although slippers made in accordance with the teachings of this patent have exhibited substantial tear resistance relative to prior art devices, some difficulties have been experienced. For example, the presence of the seam on the slipper sole has resulted in some increase in the tendency of slippers to skid on very smooth surfaces which can present a substantial hazard for some users. Also, the use of two flat blanks heat-sealed along the slipper sole provides little excess material to accomodate wider feet; thus, slipper failure due to excessive stretching on such feet has been noted. Finally, the slippers of U.S. Pat. No. 3,426,454 occasionally tend to slip off the wearer's heel, apparently due to their rather low heel or to a lack of width in the sole.
In view of the above, it is clear that a need exists for simple, inexpensive, sanitary slippers of a type which exhibits high resistance to tearing of the material, to skidding on smooth surfaces and to inadvertent slipping from the wearer's heel.